Method an apparatus for controlling unmanned aerial vehicle to land on landing platform

ABSTRACT

A method and an apparatus for controlling an unmanned aerial vehicle (UAV) to land on a landing platform are provided. The method includes: receiving a landing preparatory signal instructing the UAV to enter into a landing preparatory state; monitoring the landing platform to generate a monitoring signal in response to the landing preparatory signal; and determining whether to control the UAV to enter into a landing mode based on the monitoring signal.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to Chinese patent application No. 201610346128.2 field on May 23, 2016, and Chinese patent application No. 201610802445.0 filed on Sep. 5, 2016, the entire contents of which are incorporated herein by reference.

TECHNICAL FIELD

The present disclosure generally relates to a method and an apparatus for controlling an unmanned aerial vehicle (UAV) to land on a landing platform.

BACKGROUND

With the continuous development of aviation technology, unmanned aerial vehicles (UAVs) have been widely used in military and civilian fields. A variety of techniques have been developed in connection with the operation of the UAVs, including take-off, flight, and landing. Generally, a skilled user controls landing of a multi-rotor UAV by manipulating a remote control device associated with the multi-rotor UAV. During landing, in order to make the UAVs' landing safe and smooth, the skilled user is required to control the UAVs' attitude balance and propulsion power output.

In addition, as the UAV is usually controlled to land on ground, the UAV will be stained with dust, soil or water on the ground and the user needs to pick up the UAV from the ground.

SUMMARY

An example method for controlling an unmanned aerial vehicle (UAV) to land on a landing platform is provided. The method includes: receiving a landing preparatory signal instructing the UAV to enter into a landing preparatory state; monitoring the landing platform to generate a monitoring signal in response to the landing preparatory signal; and determining whether to control the UAV to enter into a landing mode based on the monitoring signal.

An example apparatus for controlling a UAV to land on a landing platform is provided. The apparatus includes: a receiving unit configured to receive a landing preparatory signal instructing the UAV to enter into a landing preparatory state; a monitoring unit configured to monitor the landing platform to generate a monitoring signal in response to the landing preparatory signal; and a control unit configured to determine whether to control the UAV to enter into a landing mode based on the monitoring signal.

Further, another example apparatus for controlling a UAV to land on a landing platform is provided. The apparatus includes: a processor; and a memory for storing instructions executable by the processor, wherein, when executing the instruction, the processor is configured to: receive a landing preparatory signal instructing the UAV to enter into a landing preparatory state; monitor the landing platform to generate a monitoring signal in response to the landing preparatory signal; and determine whether to control the UAV to enter into a landing mode based on the monitoring signal.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only, and are not restrictive of the invention. Further, the accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description, serve to explain principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate solutions of embodiments of the present disclosure, the drawings which are required to be used in the embodiments will be briefly described below. It should be understood that the following drawings show only certain embodiments of the present disclosure, and the scope of the disclosure is limited thereto. It also should be understood other related drawings may be obtained by those skilled in the art from the drawings without departing from the scope of the present disclosure.

FIG. 1 illustrates a diagram of an exemplary UAV landing system environment within which embodiments of the disclosure may be practiced.

FIG. 2 is a block diagram of the UAV in the landing system environment of FIG. 1.

FIG. 3 is a flow chart of an exemplary method for controlling the UAV to land on a landing platform according to an embodiment.

FIG. 4 is a flow chart of an exemplary method for controlling the UAV to land on a landing platform according to another embodiment.

FIG. 5 is a flow chart of an exemplary method for controlling the UAV to land on a landing platform according to another embodiment.

FIG. 6 is a block diagram of an exemplary landing control apparatus in the UAV as shown in FIG. 2.

FIG. 7 is a flow chart of an exemplary method for controlling the UAV to land on a landing platform according to another embodiment.

FIG. 8 is a block diagram of an exemplary landing control apparatus according to another embodiment.

The same reference numbers will be used throughout the drawings to refer to the same or like parts.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the disclosure will be described, by way of example only, with reference to the accompanying drawings. The described embodiments are only a part of the embodiments of the present disclosure, but not all of the embodiments. The components of embodiments of the present disclosure, which are generally described and illustrated in the accompanying drawings, may be arranged and designed in a variety of different configurations. Accordingly, the following detailed description of embodiments of the disclosure provided in the drawings is not intended to limit the scope of the claimed disclosure, but merely to indicate selected embodiments of the disclosure. All other embodiments obtained by those skilled in the art without the inventive effort are within the scope of the present disclosure.

It should be noted the same reference numbers will be used throughout the drawings to refer to the same or like parts. Thus, once an item is defined in a drawing, it is not necessary to further define and explain it in the subsequent drawings. It should be noted that relational terms, such as first and second, are used solely to a separate operating entity from another entity, and do not necessarily require or imply that the actual such relationship or order exist between these entities or operations.

FIG. 1 illustrates a diagram of an exemplary UAV landing system environment.

As shown in FIG. 1, a landing control apparatus 100, a UAV 200 and a remote controller 300 are provided in the UAV landing system environment. A user may send instructions to the UAV 200 through a button on the remote controller 300. The remote controller 300 may be a mobile phone, a computer, a remote control and other terminal equipment. In other embodiments, the user may also send instructions to the UAV 200 through voice commands, gesture commands or the like. The landing control apparatus 100 may be mounted on the UAV 200 to control the UAV 200 to land on a landing platform.

FIG. 2 is a block diagram schematically illustrating the UAV 200 in the environment of FIG.1.

As depicted in FIG.2, the UAV 200 includes a memory 210, a processor 220, an input and output (I/O) unit 230, a function device 240 and a power unit 250. The memory 210, the processor 220, the I/O unit 230, the function device 240 and the power unit 250 are directly or indirectly connected to each other to achieve data transmission or exchange. For example, these elements may be electrically connected to each other via one or more communication buses or signal lines. The landing control apparatus 100 may include at least one software function module in a form of software or firmware stored in the memory 210 or the processor 220. The processor 220 is used for performing executable modules stored in the memory 210, such as software modules or computer programs included in the landing control apparatus 100. After receiving the execution instruction, the processor 220 executes programs included in executable software function module. The method executable by the UAV disclosed in any embodiment of the present disclosure can be applied in the processor 220, or implemented by the processor 220.

The memory 210 is used to store various types of data of the UAV 200. The memory 210 may be an internal memory of the UAV 200, or a removable memory. For example, the memory 210 may be, but not limited to, random access memory (RAM), read only memory (ROM), programmable read-only memory (PROM), erasable read only memory (EPROM), electrically erasable read only memory (EEPROM) and the like.

The processor 220 may be an integrated circuit chip with the signal processing capability. The processor 220 as described may be a general purpose processor, including a central processor (CPU), a network processor (NP). The processor 220 can also be a digital signal processor (DSP), application specific integrated circuit (ASIC), Field-programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components. The processor 220 can execute or implement methods, steps and logic diagrams disclosed in embodiments of the present disclosure. The processor 220 may be a microprocessor or any conventional processor, etc.

The I/O unit 230 is used to receive data transmitted through wire or wireless path from a control terminal of the UAV 200, or the I/O unit 230 is used to transmit data of the UAV 200 through wire or wireless path to the control terminal of the UAV 200, so as to achieve interactions between the control terminal and the UAV 200.

The function device 240 may include a distance monitoring module, an ultrasonic sensor, an image capturing device, a speed monitoring module, an LED light and the like. The function device is used for the UAV 200 performing specific missions (for example, monitoring the landing platform, taking pictures, flashing lights, etc.)

The power unit 250 may include an electronic speed governor, a motor, a rotor and the like. The electronic speed governor is electrically connected with the motor, and the rotor is mounted on the motor. The electronic speed governor may receive a signal transmitted from the processor 220 and control the motor to rotate, so as to drive the rotor to rotate. The electronic speed governor may obtain a rotation speed of the motor, and feed back the rotation speed of the motor to the landing control apparatus 100.

In some embodiments, the UAV 200 may have more or fewer components than those described above, but the present disclosure is not limited herein.

FIG. 3 illustrates a flow chart of a method for controlling the UAV 200 of FIG. 1 to land on a landing platform according to an embodiment. Referring to FIG. 3, the method includes Steps S310-S330.

In Step S310, a landing preparatory signal is received, wherein the landing preparatory signal is used to instruct the UAV 200 to enter into a landing preparatory state.

In some embodiments, the user may send a landing preparatory signal to the UAV 200. The landing preparatory signal may be input by the user triggering a button on the remote controller 300, sending a voice command, performing a specific action in a capturing area of an image capturing device mounted on the UAV 200, or the like. The inputting manner of the landing preparatory signal is not limited by embodiments of the present disclosure.

Specifically, as to inputting the landing preparatory signal by triggering a button on a remote controller, the user may trigger the button on the remoter controller 300 of FIG. 1 to generate the landing preparatory signal. Then, the landing preparatory signal is transmitted to the UAV 200 through a wireless network and is received by an antenna of the UAV 200. In an embodiment, the landing preparatory signal is triggered in a one-touch triggering manner, that is, the user only needs to touch one button on the remote controller 300 to trigger the landing preparatory signal, and then the UAV 200 may automatically perform subsequent actions.

As to inputting the landing preparatory signal by voice control, the UAV 200 may directly receive a specific voice command (for example, “landing preparation”, “preparation for landing”, etc.) input by the user. The UAV 200 may receive the voice command through a voice sensor, convert the voice command to a landing preparatory signal and transmit the landing preparatory signal to the landing control apparatus 100.

As to inputting the landing preparatory signal through a specific gesture, the user may perform a specific action (for example, swinging his palm up and down, or other gestures) in a capturing area of an image capturing device mounted on the UAV 200. The image capturing device may take the recognized specific action as the landing preparatory signal, and send the landing preparatory signal to the landing control apparatus 100.

Further, in some embodiments, before the user sends the landing preparatory signal to the UAV 200, the UAV 200 may be positioned at a preset position with a preset landing height. For example, the remote controller 300 may be used to control the UAV 200 to fly to the preset landing height, such as a height similar to the head of the user (e.g., 2 meters from the ground, etc.), and the UAV 200 will be controlled to hover to get ready for landing. The preset landing height can be set according to actual needs, and is not limited by the above embodiments.

In some embodiments, the landing preparatory signal is send to the UAV 200 first, and after receiving the landing preparatory signal, the UAV 200 will enter into a standby state. Then the UAV 200 is controlled to fly to a preset position with the preset landing height. For example, when the user inputs the landing preparatory signal in the voice control manner, the UAV 200 is initially flying at a relatively high height. Then the user may use the remote controller 300 to control the UAV 200 to fly down to the preset position with the preset landing height, and to stay in a hovering state. In some embodiments, after receiving the landing preparatory signal, the UAV 200 still responds to control instructions sent by the remote controller 300. The actions performed by the UAV 200 are not limited by embodiments of the present disclosure. For example, the UAV 200 may perform a landing operation in response to an instruction sent by the remote controller 300, yet does not stay in a hovering state.

Before receiving the landing preparatory signal, the UAV 200 may be in a descending state, a hovering state, a flying state or other states, which is not limited by embodiments of the present disclosure.

Further, after receiving the landing preparatory signal, the UAV 200 enters into a landing preparatory state. In the landing preparatory state, the UAV 200 may send a warning signal to remind the user that the UAV 200 has entered into the landing preparatory state. In some embodiments, a warning device may be an existing LED lamp mounted on the UAV 200. For example, when the UAV 200 is in a normal flight, the LED lamp is green, but after the UAV 200 receives the landing preparatory signal and enters the landing preparatory state, the LED lamp becomes red and flashes. In some embodiments, the warning device may be a warning lamp other than the existing LED lamp, or a voice alarm. Taking a warning lamp as an example, when the UAV 200 is in a normal flight, the warning lamp is green, but after the UAV 200 receives the landing preparatory signal and enters the landing preparatory state, the warning lamp becomes red and flashes. Taking a voice alarm as an example, after the UAV 200 receives the landing preparatory signal and enters the landing preparatory state, the voice alarm may send a voice signal, such as “landing is about to take place”, etc. It should be noted that the warning system can be set according to actual needs, and the person skilled in the art can change the warning mode of the warning system.

As shown in FIG. 3, in Step S320, it monitors the landing platform to generate a monitoring signal in response to the landing preparatory signal.

The landing platform may be a palm of the user's hand or other platforms (for example, a plate, a book or other objects held by the user). The landing platform may stay below the UAV 200 at all time, or it may be merely moved below the UAV 200 by the user at an appropriate time for the landing of the UAV 200.

In step S320, the landing platform is monitored to generate a monitoring signal, which is used to determine whether the landing platform is ready for landing.

Specifically, a distance monitoring module, a speed monitoring module, an image acquiring module or an inertial measurement module mounted on the UAV 200 may be employed to monitor the landing platform and generate a monitoring signal.

For example, the distance monitoring module or the image acquiring module may be controlled to detect a vertical distance between the UAV 200 and the landing platform, and the speed monitoring module may be controlled to detect a speed variation of the UAV 200 with respect to the landing platform. Then, the vertical distance between the UAV 200 and the landing platform, and the speed variation of the UAV 200 with respect to the landing platform may be taken as the monitoring signal.

In Step S330, it is determined whether to control the UAV 200 to enter into a landing mode based on the monitoring signal.

Specifically, in Step S330, it is determined whether the landing platform meets a preset condition based on the monitoring signal. The preset condition indicates the landing platform is ready for landing the UAV 200. For example, the preset condition may indicate that a vertical distance between the UAV 200 and the landing platform is smaller than or equal to a preset threshold distance, or a speed variation of the UAV 200 with respect to the landing platform is greater than a preset speed variation threshold. If the monitoring signal indicates the landing platform meets the preset condition, it is determined the landing platform has been prepared for landing, and the UAV 200 is controlled to enter into the landing mode.

In some embodiments, the UAV 200 includes at least one rotor. During the landing mode, the landing control apparatus 100 may control the at least one rotor of the UAV 200 to stop rotating, such that the UAV 200 lands on the landing platform in a free-fall manner. In some embodiments, the landing control apparatus 100 may control the at least one rotor of the UAV 200 to rotate at a smaller speed, such that the UAV 200 lands on the landing platform at a predetermined speed. In the above embodiments, in the landing mode, all the rotors of the UAV 200 are controlled to stop rotating or rotate at a smaller speed. The UAV 200 may include one or more rotors. That is, the one or more rotors of the UAV 200 are all controlled to stop rotating or rotate at a smaller speed. After the UAV 200 has landed on the landing platform, the landing control apparatus 100 control the at least one rotor of the UAV 200 to stop rotating. Further, during the landing mode, the landing control apparatus 100 may also change a flying attitude of the UAV 200, and then control the UAV 200 to land on the landing platform. It could be understood that, the above-mentioned embodiments are merely specific embodiments, and may be modified according to actual needs.

FIG. 4 illustrates a flow chart of another exemplary method for controlling the UAV 200 of FIG. 1 to land on a landing platform according to another embodiment of the present disclosure.

Step S410 in FIG. 4 is substantially identical to Step S310 in FIG. 3, which will not be elaborated here.

In Step S420, a vertical distance between the UAV 200 and the landing platform is monitored.

In one example, a distance monitoring module may be employed to monitor the landing platform. Specifically, after receiving the landing preparatory signal, the distance monitoring module is controlled to monitor a vertical distance, for example, a vertical distance from the ground to the UAV 200. When the user places a landing platform below the UAV 200, the vertical distance below the UAV 200 is reduced quickly (e.g., the vertical distance is changed from a distance between the UAV 200 and the ground to a distance between the UAV 200 and the landing platform). After obtaining the updated vertical distance between the UAV 200 and the landing platform, the distance monitoring module transmits the vertical distance to the landing control apparatus 100. In this embodiment, the vertical distance between the UAV 200 and the landing platform is a distance in vertical direction between the UAV 200 and the landing platform. The vertical distance itself might be used as the monitoring signal.

In another example, a distance monitoring module, such as an ultrasonic sensor which has limits of its measuring capability, is employed to monitor the landing platform. The ultrasonic sensor has a lower limit of measuring capability, and will output an invalid signal to indicate that an object is within its minimum measuring distance. When the user places the landing platform below the UAV 200 and the distance between the UAV 200 and the landing platform is smaller than the minimum measuring distance, the ultrasonic sensor cannot output an effective measured distance, but outputs an invalid signal. Thus, in this embodiment, the invalid signal may be used as the monitoring signal.

In another example, an image acquiring module is employed to monitor the landing platform. The image acquiring module may be a binocular camera or a monocular camera, and may be disposed directly below the UAV 200. The image acquiring module is used to acquire and output an image of the landing platform. When the user places the landing platform below the UAV 200, if the landing platform is within the focus range of the image acquiring module, the image acquiring module can output a clear image; and if the landing platform is very close to the UAV 200 and the image acquiring module cannot focus on the landing platform, the image acquiring module outputs an unclear image. That is, the small distance between the UAV 200 and the landing platform causes loss of focus of the image acquiring module. An image corner detection method may be used to calculate a characteristic value of the image, so as to determine whether the distance between the UAV 200 and the landing platform causes the loss of focus. Thus, in this embodiment, the monitoring signal depends on whether the image output by the image acquiring module is clear.

In Step S430, it is determined whether the vertical distance between the UAV 200 and the landing platform is smaller than or equal to a preset threshold distance.

If the vertical distance between the UAV 200 and the landing platform is greater than the preset threshold distance, the method goes back to Step S420.

If the vertical distance between the UAV 200 and the landing platform is smaller than or equal to the preset threshold distance, the method goes to Step S440 in which the UAV 200 is controlled to enter into the landing mode.

The preset threshold distance may be smaller than 40 cm, for example, 15 cm or 30 cm. Namely, when the distance monitoring module detects the vertical distance between the UAV 200 and the landing platform is smaller than the preset threshold distance, it is determined the landing platform has been prepared for landing, and Step S440 is performed to control the UAV 200 to enter into the landing mode.

Further, the distance monitoring module may be used to monitor a distance variation of the UAV 200 with respect to the landing platform, so as to determine whether to control the UAV 200 to enter into the landing mode. For example, before the user places the landing platform below the UAV 200, a distance between the UAV 200 and the ground is 2 m, but after the user places the landing platform below the UAV 200, the distance between the UAV 200 and the landing platform is 0.5 m. Thus, the distance variation monitored by the distance monitoring module is 1.5 m. If it is determined the distance variation is greater than a preset distance variation threshold, the UAV 200 may be controlled to enter into the landing platform.

In another example, when the ultrasonic sensor is employed to monitor the landing platform, it is determined whether the ultrasonic sensor outputs an invalid signal. Specifically, when the vertical distance between the UAV 200 and the landing platform is within the measuring range of the ultrasonic sensor, the ultrasonic sensor may output an effective (i.e., valid) distance. When the vertical distance between the UAV 200 and the landing platform is out of the measuring range of the ultrasonic sensor, the ultrasonic sensor cannot output an effective distance, but outputs an invalid signal. If the output of the ultrasonic sensor is changed from the effective distance to the invalid signal, it can be determined the landing platform has been prepared for landing, and Step S440 is performed to control the UAV 200 to enter into the landing mode.

In another example, when the image acquiring module is employed to monitor the landing platform, it is determined whether the image of the landing platform output by the image acquiring module meets a predetermined criterion. Specifically, when the landing platform is very close to the UAV 200, the image acquiring module cannot focus on the landing platform and cannot output a clear image meeting the predetermined criterion. Thus, when the image output by the image acquiring module doesn't meet the predetermined criterion because the landing platform becomes an obstacle of the imaging module, it is determined the landing platform has been prepared for landing, and Step S440 is performed to control the UAV 200 to enter into the landing mode.

In Step S440, the UAV 200 is controlled to enter into the landing mode, after it is determined the vertical distance between the UAV 200 and the landing platform is smaller than or equal to the preset threshold distance.

More details about Step S440 may refer to the description of Step S330 in FIG. 3, and is not described in detail herein.

FIG. 5 illustrates a flow chart of another exemplary method for controlling the UAV 200 of FIG. 1 to land on a landing platform according to another embodiment of the present disclosure.

Step S510 in FIG. 5 is substantially identical to Step S310 in FIG. 3, which will not be elaborated here.

In Step S520, a speed variation of the UAV 200 with respect to the landing platform is monitored.

In one example, a speed monitoring module is employed to monitor speed variation of the UAV 200, e.g., with respect the landing platform. The speed monitoring module may be used to monitor a vertical descending speed of the UAV 200. Specifically, the speed monitoring module may be used to monitor a vertical descending speed of the UAV 200 with respect to the landing platform. The vertical descending speed of the UAV 200 is a speed of the UAV 200 in the vertical downward direction. In a process the UAV 200 is descending at a preset speed, if the user places the landing platform below the UAV 200 and holds up the descending UAV 200 quickly, the UAV 200 contacts the landing platform and there will be a sudden change in the vertical descending speed of the UAV 200. Moreover, the airflow generated by the rotor of the UAV 200 may also be reflected by the landing platform, and has a reverse effect on the descending of the UAV 200. Thus, a downward acceleration of the UAV 200 may be abruptly reduced, or even changed into an upward acceleration. It should be noted that, the sudden change of the vertical descending speed refers to a situation that the vertical descending speed of the UAV 200 changes from the preset descending speed to a speed smaller than a threshold speed, for example, 0.05 m/s.

In some embodiments, the speed monitoring module may be an acceleration monitoring module, a GPS sensor, an ultrasonic sensor, a barometer or the like. For example, the vertical descending speed of the UAV 200 may be obtained by accelerometer integration. Since a drift problem is present in the accelerometer, a long integration process will lead to a big deviation to the speed. Thus, other sensors may be used to address the deviation. For example, an instantaneous motion speed of the UAV 200 can be obtained through GPS, an ultrasonic sensors or a barometer are used to address the integration deviation of the accelerometer to get a more accurate speed of the UAV 200. Specific adaptions may be implemented by Kalman filter algorithm. Kalman filter algorithm would give a better estimate of the vertical descending speed of the UAV 200 by combining instantaneous vertical descending speed outputs from the accelerometer, the GPS and the ultrasonic sensors. In this embodiment, the vertical descending speed of the UAV 200 is the monitoring signal.

In Step S530, it is determined whether a speed variation of the UAV 200 with respect to the landing platform is greater than a preset speed variation threshold.

If the speed variation of the UAV 200 with respect to the landing platform is smaller than or equal to a preset speed variation threshold, it goes back to Step S520.

If the speed variation of the UAV 200 with respect to the landing platform is greater than a preset speed variation threshold, Step S540 is performed.

In one example, when the speed monitoring module is employed to monitor the landing platform, it is determined whether the speed variation of the UAV with respect to the landing platform is greater than a preset speed variation threshold. Specifically, if the user places the landing platform below the UAV 200 and holds up the descending UAV 200 quickly, the UAV 200 contacts the landing platform and there will be a sudden change in the vertical descending speed of the UAV 200. The speed monitoring module may output a speed variation of the UAV with respect to the landing platform. Thus, when the speed variation of the UAV with respect to the landing platform is greater than the preset speed variation threshold, it is determined the landing platform has been prepared for landing, and Step S540 is performed to control the UAV 200 to enter into the landing mode. In this case, when the UAV 200 contacts the landing platform, the landing control apparatus 100 may directly control the at least one rotor of the UAV 200 to stop rotating during the landing mode.

In Step S540, the UAV 200 is controlled to enter into the landing mode, after it is determined the speed variation of the UAV 200 with respect to the landing platform is greater than the preset speed variation threshold.

More details about Step S540 may refer to the description of Step S330 in FIG. 3, and is not described in detail herein.

It should be noted that, the distance monitoring module, the speed monitoring module, the image acquisition module and the like are only specific examples. The present disclosure is not limited by the above embodiments. Other monitoring methods may also be employed as long as it can be determined whether the landing platform meets the preset condition. Moreover, in the above steps for determining whether the landing platform meets the preset conditions, if any one (or one specific) of the preset conditions is met, the landing platform is determined to be prepared, and the UAV 200 is controlled to enter into the landing mode.

In addition to the flow charts shown in FIGS. 3, 4 and 5, the present disclosure also incorporates certain mechanisms/steps for UAV's safety considerations, e.g., interruption of landing operation, restoring the hovering state or flying mode, as described in details below.

In some embodiments, after the UAV 200 enters into the landing mode, the landing control apparatus 100 continues to monitor the vertical distance between the UAV 200 and the landing platform. If the vertical distance between the UAV 200 and the landing platform is greater than the preset threshold distance, the UAV 200 is controlled to return to a hovering mode or a flying mode.

In an example, after the UAV 200 is controlled to enter into the landing mode, the distance monitoring module is further controlled to monitor the vertical distance between the UAV 200 and the landing platform. When the vertical distance between the UAV 200 and the landing platform is greater than the preset threshold distance, the landing control apparatus 100 may determine the landing platform has been removed/withdrawn or is no longer suitable for landing, and it increases the rotation speed of the rotor to control the UAV to return to a hovering mode or a flying mode, so as to avoid accidents. In some embodiments, the preset threshold distance may be smaller than 40 cm, for example, 15 cm.

In another example, after the UAV 200 is controlled to enter into the landing mode, the ultrasonic sensor is further controlled to monitor the vertical distance between the UAV 200 and the landing platform. When the vertical distance between the UAV 200 and the landing platform is greater than the minimum measuring distance of the ultrasonic sensor, the output of the ultrasonic sensor changes from an invalid signal to an effective distance. Accordingly, the landing control apparatus 100 may determine the landing platform has been removed/withdrawn or is no longer suitable for landing, and it increase the rotation speed of the rotor to control the UAV to return to a hovering mode or a flying mode.

In another example, after the UAV 200 is controlled to enter into the landing mode, the image acquiring module is further controlled to output the image of the landing platform. When the image of the landing platform meets the predetermined criterion, the landing control apparatus 100 may determine the distance between the UAV 200 and the landing platform becomes large, and the landing platform has been removed/withdrawn or is no longer suitable for landing. Thus, the landing control apparatus 100 may increase the rotation speed of the rotor to control the UAV 200 to return to a hovering mode or a flying mode.

In some embodiments, after the UAV 200 enters into the landing mode, the landing control apparatus 100 monitors a tilting angle of the UAV 200. If the tilting angle of the UAV 200 is greater than a preset threshold angle, the UAV 200 is controlled to return to a hovering mode or a flying mode.

In an example, after the UAV 200 is controlled to enter into the landing mode, a real-time detection of altitude of the UAV 200 is performed to get a tilting angle of the UAV 200. Specifically, the altitude of the UAV 200 can be detected by an inertial measurement unit (IMU) including gyroscopes and accelerometers. When the tilting angle of the UAV 200 is greater than a preset threshold, the landing control apparatus 100 may increase the rotation speed of the rotor to control the UAV 200 to return to a hovering mode or a flying mode. The threshold may be set according to actual needs, such as 60 degrees. When there is a tilt or a flip to the UAV 200 exceeding the threshold, the landing control apparatus 100 increases the rotation speed of the rotor, thus stopping the process of landing.

FIG. 6 provides a schematic view of the structure of the landing control apparatus 100 shown in FIG. 1 and FIG. 2.

As shown in FIG. 6, the landing control apparatus 100 may include a receiving unit 610, a monitoring unit 620 and a control unit 630.

The receiving unit 610 is configured to receive a landing preparatory signal instructing the UAV 200 to enter into a landing preparatory state.

In some embodiments, the user may send a landing preparatory signal to the UAV 200. The landing preparatory signal refers to an instruction from the user that instructs the UAV 200 to enter into a landing preparatory state. The landing preparatory signal may be input by the user triggering a button on the remote controller 300, sending a voice command, performing a specific action in a capturing area of an image capturing device mounted on the UAV 200, or the like. Then, an antenna, a voice sensor or an image capturing device mounted on the UAV 200 may be employed to receive the landing preparatory signal. Thus the receiving unit 610 receives the landing preparatory signal from the antenna, the voice sensor or the image capturing device.

The monitoring unit 620 is configured to monitor the landing platform to generate a monitoring signal in response to the landing preparatory signal.

In some embodiments, the monitoring unit 620 may control a distance monitoring module, a speed monitoring module, an image acquiring module or an inertial measurement module mounted on the UAV 200 (now shown in FIG. 6) to monitor the landing platform and generate a monitoring signal. The distance monitoring module may be an ultrasonic sensor, a laser distance measuring sensor, an infrared distance measuring sensor or the like mounted on the UAV 200.

When the distance monitoring module or the image acquiring module is employed to monitor the landing platform, a vertical distance between the UAV 200 and the landing platform may be detected. The vertical distance between the UAV 200 and the landing platform is taken as the monitoring signal to indicate whether the landing platform meets a preset condition indicating whether the landing platform is ready for landing the UAV 200.

When the speed monitoring module is employed to monitor the landing platform, a speed variation of the UAV 200 with respect to the landing platform may be detected. The speed variation of the UAV 200 with respect to the landing platform is taken as the monitoring signal to indicate whether the landing platform meets a preset condition.

The control unit 630 is configured to determine whether to control the UAV 200 to enter into a landing mode based on the monitoring signal.

In some embodiments, the control unit 630 may be a flying controller of the UAV 200. The control unit 630 is configured to determine whether the landing platform meets the preset condition based on the monitoring signal. For example, the preset condition may be that a vertical distance between the UAV 200 and the landing platform is smaller than or equal to a preset threshold distance, or that a speed variation of the UAV 200 with respect to the landing platform is greater than a preset speed variation threshold. If the monitoring signal from the monitoring module 620 indicates the landing platform meets the preset condition, the control unit 630 determines the landing platform has been prepared for landing, and controls the UAV 200 to enter into the landing mode.

For example, the control unit 630 may be configured to control the UAV 200 to enter into the landing mode when the vertical distance between the UAV 200 and the landing platform is smaller than or equal to the preset threshold distance, or when the speed variation of the UAV 200 is greater than the preset speed variation threshold.

In some embodiments, the UAV 200 includes at least one rotor. During the landing mode, the control unit 630 is further configured to control the at least one rotor of the UAV 200 to stop rotating, such that the UAV 200 lands on the landing platform in a free-fall manner.

In some embodiments, the control unit 630 is further configured to control the at least one rotor of the UAV 200 to rotate at a smaller rotation speed, such that the UAV 200 lands on the landing platform at a predetermined speed. After the UAV 200 has landed on the landing platform, the control unit 630 is configured to control the at least one rotor of the UAV 200 to stop rotating.

In addition, in some embodiments, for safety considerations, after the UAV 200 enters into the landing mode, the monitoring unit 620 is further configured to continue to monitor the vertical distance between the UAV 200 and the landing platform, and the control unit 630 is further configured to control the UAV 200 to return to a hovering mode or a flying mode, e.g., when the vertical distance between the UAV 200 and the landing platform is greater than the preset threshold distance.

In some embodiments, after the UAV 200 enters into the landing mode, the monitoring unit 620 is further configured to monitor a tilting angle of the UAV 200, and the control unit 630 is further configured to control the UAV 200 to return to a hovering mode or a flying mode, when the tilting angle of the UAV 200 is greater than a preset threshold angle.

More details about the landing control apparatus 100 may refer to the description of the above method, and is not described in detail herein.

In addition to the above monitoring/landing/determination operations related to FIG. 3-5, the present invention also proposes a more comprehensive landing control process. Referring to FIG. 7, a flow chart of an exemplary method for controlling an UAV 200 to land on a landing platform is illustrated according to another embodiment. The method includes Steps S710-S790.

In Step S710, a landing preparatory signal is received, wherein the landing preparatory signal is used to instruct the UAV 200 in FIG. 1 to enter into a landing preparatory state.

Step S710 is substantially identical to Step S310 of FIG. 3, and will not be elaborated here.

In Step S720, a current height of the UAV 200 is obtained.

The current height of the UAV 200 may be a relative height, such as a vertical distance between the current position of the UAV 200 and the landing location. Or, the current height can be an absolute height, if desired. Further, the current height of the UAV 200 may be monitored in real time according to a preset program, or may be obtained after receiving the landing preparatory signal.

In Step 730, the current height of the UAV 200 is compared with a first preset height, and it is determined whether the current height of the UAV is greater than the first preset height.

The first preset height may be set according to actual needs. In some embodiment, the first preset height ranges from 1.5 m to 3 m. For example, the first preset height may be 2.2 m.

If the current height of the UAV 200 is greater than the first preset height, the method goes to Step 740, wherein a first preset descending process may be performed.

In Step S740, the first preset descending process is performed. That is, the UAV 200 is controlled to fly to the first preset height at a first descending speed.

If the current height of the UAV 200 is smaller than or equal to the first preset height, the method goes to Step S750, wherein the current height of the UAV 200 is further compared with a second preset height.

In Step S750, the current height of the UAV 200 is further compared with a second preset height, and it is determined whether the current height of the UAV 200 is greater than the second preset height.

The second preset height is smaller than the first preset height, and can be set according to actual needs, such as structural characteristics of the UAV 200. In some embodiments, the second preset height ranges from 0.5 m to 1.5 m. For example, the second preset height may be 0.9 m.

If the current height of the UAV 200 is greater than the second preset height, the method goes to Step 760, wherein a second preset descending process may be performed.

If the current height of the UAV 200 is smaller than or equal to the second preset height, the method goes to Step S790, wherein the UAV 200 is controlled to enter into the landing mode.

In Step S760, the second preset descending process is performed. That is, the UAV 200 is controlled to fly to the second preset height at a second descending speed, wherein the second descending speed is smaller than the first descending speed.

In above steps, different preset descending processes may be performed according to different heights of the UAV 200 obtained in Step S720.

Specifically, when the flying height of the UAV 200 is higher than the first preset height, it is determined the UAV 200 is at a relatively high position, and thus the UAV 200 performs a first preset descending process. The first preset descending process can control the UAV 200 to fly to the first preset height at a relatively fast speed, so as to reduce the time of the landing process. The program of the first preset descending process may be stored in the UAV 200 in advance, in the remote controller 300 shown in FIG. 1 or be available from online storage, which can be determined according to actual needs.

The first descending speed may be a vertical descending speed of the UAV 200, or a speed at which the UAV 200 flies to the landing location, which can be determined according to actual needs. The first descending speed may be set by the control unit 630. In this embodiment, the first descending speed is a vertical descending speed of the UAV 200, and the UAV 200 is controlled to descend at the first descending speed until it reaches the first preset height. The first descending speed ranges from 0.2 m/s to 1 m/s, which can be determined according to actual need. For example, the first descending speed may be 0.5 m/s.

Further, when the flying height of the UAV 200 is lower than the first preset height, or when the current height of the UAV 200 obtained in Step S710 is lower than the first preset height, the UAV 200 performs the second preset descending process, so as to control the UAV 200 to descend at the second descending speed. Specifically, the rotation speed of the rotor of the UAV 200 is decreased to control the UAV 200 to descend at the second descending speed.

The second descending speed is smaller than the first descending speed. The magnitude of the second descending speed may be determined according to the second preset height. Specifically, when the second preset height is relatively high, namely, when the UAV 200 is at a relatively high height, the second descending speed is selected to be relatively low. When the second preset height is relatively low, namely, when the UAV 200 is at a relatively low height, the second descending speed is selected to be relatively high. Thus, safety concerns to the UAV 200 during landing and the long time of the landing process can both be addressed.

In some embodiments, the second descending speed may range from 0.1 m/s to 0.5 m/s, and can be determined according to actual needs. In this embodiment, the second descending speed is 0.1 m/s, so as to ensure the user has enough time to put out his palm or set the landing platform, and avoid fast speed collision on the user palm or the landing platform.

In some embodiments, the second descending process may further include changing a flying attitude of the UAV 200. For example, the second descending process may control the UAV 200 to perform landing preparation operation, such as putting down the landing support and retracting the sensors. In addition, the second descending process may control monitoring devices on the UAV 200 to monitor surrounding environment, and determine whether the surrounding environment is suitable for landing. It could be understood that, when the surrounding environment is suitable for landing, the second descending process can directly control the UAV 200 to land on the landing platform.

In some embodiments, when the UAV 200 is controlled to fly to the first preset height at the first descending speed, the UAV 200 may send a landing reminder to the user to remind the user to prepare the landing platform.

Specifically, the UAV 200 may set a landing wait signal, so as to indicate the UAV 200 has entered into a landing wait stage. When entering into the landing wait stage, the UAV 200 may transmit a landing-platform preparatory signal wirelessly to the remote controller 300 through an instruction transmitting module, so as to control the remote controller 300 to output the landing-platform preparatory signal. The landing-platform preparatory signal indicates that the UAV 200 has entered into the landing wait stage, and reminds the user to put out his hand or prepare other landing platform. The remote controller 300 may remind the user the UAV 200 has entered into the landing wait stage through lighting, sounds, images, vibrations, and other means.

In Step S770, it monitors the landing platform to generate a monitoring signal in response to the landing preparatory signal.

Step S770 is substantially identical to Step S320 of FIG. 3, and will not be described in detail herein.

In Step S780, it is determined whether the landing platform meets a preset condition based on the monitoring signal, wherein the preset condition is used to indicate whether the landing platform is ready for landing the UAV 200.

As described above, the preset condition may be one of the following: a vertical distance between the UAV 200 and the landing platform being smaller than or equal to a preset threshold distance, or a speed variation of the UAV 200 with respect to the landing platform being greater than a preset speed variation threshold.

If the monitoring signal indicates the landing platform meets the preset condition, the method goes to Step S790, wherein the UAV 200 is controlled to enter into a landing mode. Otherwise, the method goes back to Step S770.

More details about Step S780 may refer to the descriptions of Step S430 in FIG. 4 and Step S530 in FIG. 5, and are not described in detail herein.

In Step S790, the UAV 200 is controlled to enter into the landing mode.

Step S790 is substantially identical to Step S440 in FIG. 4 and Step S540 in FIG. 4, and will not be described in detail herein.

It should be noted that, in Step S750, if it is determined the current height of the UAV 200 is smaller than or equal to the second preset height, it goes to Step S790, wherein the UAV 200 is directly controlled to enter into the landing mode.

Additionally or optionally, in Step S790, a third preset descending process may be performed.

Specifically, the third descending process may control the UAV 200 to land on the landing platform at a predetermined speed or in a free-fall manner. In some embodiments, the third descending process may control the UAV 200 to descend at a third descending speed. The third descending speed may be greater or smaller than the second descending speed. In some embodiments, in the descending process of the UAV 200, the descending speed of the UAV 200 may be monitored in real time. When the descending speed of the UAV 200 is detected to be smaller than 0.1 m/s in a preset period, the rotor of the UAV 200 may be controlled to stop rotating, and the landing process is completed. In some embodiments, the third preset landing process may turn off the power unit of the UAV 200. Thus, the rotor of the UAV 200 is controlled to stop rotating, such that the UAV 200 may descend in a free-fall manner. In this case, the free-fall speed may be greater than the second descending speed.

Referring to FIG. 8, a block diagram of the landing control apparatus shown in FIG. 1 is illustrated according to an embodiment.

As shown in FIG. 8, the landing control apparatus 100 may include a receiving unit 810, a height obtaining unit 820, a monitoring unit 830, a control unit 840 and a reminding unit. The landing control apparatus 100 may be employed to perform the method shown in FIG. 7.

The receiving unit 810 is configured to receive a landing preparatory signal, wherein the landing preparatory signal is used to instruct the UAV 200 to enter into a landing preparatory state.

The height obtaining unit 820 is configured to obtain a current height of the UAV 200.

The monitoring unit 830 is configured to monitor the landing platform to generate a monitoring signal in response to the landing preparatory signal.

The control unit 840 is configured to determine whether to control the UAV 200 to enter into a landing mode based on the monitoring signal.

The receiving unit 810, the monitoring unit 830 and the control unit 840 in FIG. 8 are substantially identical to the receiving unit 310, the monitoring unit 320 and the control unit 330 in FIG. 3, respectively. Thus, more details about the receiving unit 810, the monitoring unit 830 and the control unit 840 may refer to the receiving unit 310, the monitoring unit 320 and the control unit 330 in FIG. 3, and are not described in detail herein.

In some embodiments, the control unit 840 is further configured to: control the UAV to fly to a first preset height at a first descending speed when the current height of the UAV 200 is greater than the first preset height; and control the UAV 200 to fly to a second preset height at a second descending speed when the current height of the UAV 200 is smaller than or equal to the first preset height but is greater than the second preset height, wherein the second descending speed is smaller than the first descending speed.

In some embodiments, during controlling the UAV 200 to fly to the second preset height at the second descending speed, the control unit 840 is further configured to control the UAV 200 to enter into the landing mode if the monitoring signal indicates the landing platform meets a preset condition.

In some embodiments, the control unit 840 is further configured to control the UAV 200 to enter into the landing mode when the current height of the UAV 200 is smaller than or equal to the second preset height.

The reminding unit 850 is configured to send a landing reminder signal to a user when the control unit 840 controls the UAV 200 to fly to a first preset height at a first descending speed, wherein the landing reminder signal is used to remind the user to prepare the landing platform.

Moreover, an apparatus for controlling an unmanned aerial vehicle (UAV) to land on a landing platform is provided in embodiments of the present disclosure. The apparatus includes: a processor; and a memory for storing instructions executable by the processor, wherein, when executing the instruction, the processor is configured to: receive a landing preparatory signal instructing the UAV to enter into a landing preparatory state; monitor the landing platform to generate a monitoring signal in response to the landing preparatory signal; and determine whether to control the UAV to enter into a landing mode based on the monitoring signal.

More details about the above apparatus may refer to the description of the above method, and are not described in detail herein.

By employing the method and apparatus provided in the present application, the UAV can be controlled to land on a hand of the user or other landing platforms, the landing operations are simplified. As the UAV is controlled to land on the landing platform, the UAV will not be stained with dust, soil or water on the ground, and the user doesn't need to pick up the UAV from the ground.

Further, the landing operations can be triggered in a one-touch triggering manner. The user only needs to touch one button on the remote controller, and then the UAV 200 may automatically perform subsequent actions. Thus, a control interface of the remote controller can be simplified.

Further, after the landing preparatory signal is received, different preset descending processes may be performed according to different heights of the UAV. When the UAV is at a relatively high position, the UAV is controlled to descend at a higher speed; and when the UAV is at a relatively low position, the UAV is controlled to descend at a smaller speed. Thus, damage to the UAV during landing can be reduced or avoided, and the waiting time in the landing process can be reduced.

The apparatus and methods disclosed in the embodiments of the present disclosure can be implemented by other ways. The aforementioned apparatus embodiments are merely illustrative. For example, flow charts and block diagrams in the figures show the architecture and the function operation according to a plurality of apparatus, methods and computer program products disclosed in embodiments of the present disclosure. In this regard, each frame of the flow charts or the block diagrams may represent a module, a program segment, or portion of the program code. The module, the program segment, or the portion of the program code includes one or more executable instructions for implementing predetermined logical function. It should also be noted that in some alternative embodiments, the function described in the block can also occur in a different order as described from the figures. For example, two consecutive blocks may actually be executed substantially concurrently. Sometimes they may also be performed in reverse order, depending on the functionality. It should also be noted that, each block of the block diagrams and/or flow chart block and block combinations of the block diagrams and/or flow chart can be implemented by a dedicated hardware-based systems execute the predetermined function or operation or by a combination of a dedicated hardware and computer instructions. Further, the functional modules disclosed in embodiments of the present disclosure may be integrated together to form a separate part. Alternatively, each module can be alone, or two or more modules can be integrated to form a separate section.

If the functions are implemented in the form of software modules and sold or used as a standalone product, the functions can be stored in a computer readable storage medium. Based on this understanding, the technical nature of the present disclosure, part contributing to the prior art, or part of the technical solutions may be embodied in the form of a software product. The computer software product is stored in a storage medium, including several instructions to instruct a computer device (may be a personal computer, server, or network equipment) to perform all or part of the steps of various embodiments of the present. The aforementioned storage media include: U disk, removable hard disk, read only memory (ROM), a random access memory (RAM), floppy disk or CD-ROM, which can store a variety of program codes.

It should be noted that relational terms, such as first and second, are used solely to a separate operating entity from another entity, and do not necessarily require or imply that the actual such relationship or order exist between these entities or operations. Moreover, the term “comprising”, “including” or any other variation thereof are intended to cover a non-exclusive inclusion, such that processes, methods, articles, or apparatus including a series of factors includes not only those elements, but also includes other elements not explicitly listed, or further includes inherent factors for such processes, methods, articles or devices. Without more constraints, elements defined by the statement “includes a ” does not exclude the presence of other elements included in the processes, methods, articles or devices.

Further, other embodiments will be apparent to those skilled in the art from consideration of the specification and practice of one or more embodiments of the disclosure disclosed herein. Any modifications, equivalent substitutions, improvements and the like within the spirit and principles of the present disclosure are intended to be included within the scope of the present disclosure. It is intended, therefore, that this disclosure and the examples herein be considered as exemplary only, with a true scope and spirit of the disclosure being indicated by the following listing of exemplary claims. 

What is claimed is:
 1. A method for controlling an unmanned aerial vehicle (UAV) to land on a landing platform, comprising: receiving a landing preparatory signal instructing the UAV to enter into a landing preparatory state; monitoring the landing platform to generate a monitoring signal in response to the landing preparatory signal; and determining whether to control the UAV to enter into a landing mode based on the monitoring signal.
 2. The method of claim 1, wherein the monitoring signal indicates a vertical distance between the UAV and the landing platform; and the method further comprises: controlling the UAV to enter into the landing mode when the vertical distance between the UAV and the landing platform is smaller than or equal to a preset threshold distance.
 3. The method of claim 2, wherein the UAV comprises at least one rotor, and controlling the UAV to enter into the landing mode further comprises: controlling the at least one rotor of the UAV to stop rotating, such that the UAV lands on the landing platform in a free-fall manner.
 4. The method of claim 2, wherein the UAV comprises at least one rotor, and controlling the UAV to enter into the landing mode further comprises: controlling the at least one rotor of the UAV to rotate at a smaller rotation speed, such that the UAV lands on the landing platform at a predetermined speed.
 5. The method of claim 1, wherein the monitoring signal indicates a speed variation of the UAV with respect to the landing platform, the UAV comprises at least one rotor, and the method further comprises: controlling the at least one rotor of the UAV to stop rotating when the speed variation of the UAV with respect to the landing platform is greater than a preset speed variation threshold.
 6. The method of claim 2, wherein, after the UAV enters into the landing mode, the method further comprises: continuing to monitor the vertical distance between the UAV and the landing platform; and controlling the UAV to return to a hovering mode or a flying mode when the vertical distance between the UAV and the landing platform is greater than the preset threshold distance.
 7. The method of claim 2, wherein, after the UAV enters into the landing mode, the method further comprises: monitoring a tilting angle of the UAV; and controlling the UAV to return to a hovering mode or a flying mode when the tilting angle of the UAV is greater than a preset threshold angle.
 8. The method of claim 1, wherein, after receiving the landing preparatory signal and before monitoring the landing platform, the method further comprises: obtaining a current height of the UAV; controlling the UAV to fly to a first preset height at a first descending speed when the current height of the UAV is greater than the first preset height; or controlling the UAV to fly to a second preset height at a second descending speed when the current height of the UAV is smaller than or equal to the first preset height but is greater than the second preset height, wherein the second descending speed is smaller than the first descending speed.
 9. The method of claim 8, wherein the determining step further comprises: based on the monitoring signal, controlling the UAV to enter into the landing mode during controlling the UAV to fly to the second preset height at the second descending speed.
 10. The method of claim 8, wherein the determining step further comprises: based on the monitoring signal, controlling the UAV to enter into the landing mode when the current height of the UAV is smaller than or equal to the second preset height.
 11. The method of claim 10, wherein the UAV is controlled to descend at a third descending speed during the landing mode.
 12. The method of claim 8, wherein, when controlling the UAV to fly to the first preset height at the first descending speed, the method further comprises: sending a landing reminder signal to a user, wherein the landing reminder signal is used to remind the user to prepare the landing platform.
 13. An apparatus for controlling an unmanned aerial vehicle (UAV) to land on a landing platform, comprising: a processor; and a memory for storing instructions executable by the processor, wherein, when executing the instruction, the processor is configured to: receive a landing preparatory signal instructing the UAV to enter into a landing preparatory state; monitor the landing platform to generate a monitoring signal in response to the landing preparatory signal; and determine whether to control the UAV to enter into a landing mode based on the monitoring signal.
 14. The apparatus of claim 13, wherein the processor is further configured to control the UAV to enter into the landing mode, when the monitoring signal indicates a vertical distance between the UAV and the landing platform, and the vertical distance between the UAV and the landing platform is smaller than or equal to a preset threshold distance.
 15. The apparatus of claim 14, wherein the UAV comprises at least one rotor, and the processor is further configured to control the at least one rotor of the UAV to stop rotating, such that the UAV lands on the landing platform in a free-fall manner.
 16. The apparatus of claim 14, wherein the UAV comprises at least one rotor, and the processor is further configured to control the at least one rotor of the UAV to rotate at a smaller rotation speed, such that the UAV lands on the landing platform at a predetermined speed.
 17. The apparatus of claim 13, wherein the UAV comprises at least one rotor, and the processor is further configured to control the at least one rotor of the UAV to stop rotating when the monitoring signal indicates a speed variation of the UAV with respect to the landing platform and the speed variation of the UAV is greater than a preset speed variation threshold.
 18. The apparatus of claim 14, wherein, after the UAV enters into the landing mode, the processor is further configured to: continue to monitor the vertical distance between the UAV and the landing platform, and control the UAV to return to a hovering mode or a flying mode when the vertical distance between the UAV and the landing platform is greater than the preset threshold distance.
 19. The apparatus of claim 14, wherein, after the UAV enters into the landing mode, the processor is further configured to: monitor a tilting angle of the UAV, and control the UAV to return to a hovering mode or a flying mode when the tilting angle of the UAV is greater than a preset threshold angle.
 20. The apparatus of claim 13, wherein, after receiving the landing preparatory signal and before monitoring the landing platform, the processor is further configured to: obtain a current height of the UAV; control the UAV to fly to a first preset height at a first descending speed when the current height of the UAV is greater than the first preset height; and control the UAV to fly to a second preset height at a second descending speed when the current height of the UAV is smaller than or equal to the first preset height, but is greater than the second preset height, wherein the second descending speed is smaller than the first descending speed.
 21. The apparatus of claim 20, wherein the processor is further configured to control the UAV to enter into the landing mode based on the monitoring signal, during controlling the UAV to fly to the second preset height at the second descending speed.
 22. The apparatus of claim 20, wherein the processor is further configured to control the UAV to enter into the landing mode based on the monitoring signal, when the current height of the UAV is smaller than or equal to the second preset height.
 23. The apparatus of claim 22, wherein the processor is further configured to control the UAV to descend at a third descending speed during the landing mode.
 24. The apparatus of claim 20, wherein, when controlling the UAV to fly to a first preset height at a first descending speed, the processor is further configured to: send a landing reminder signal to a user, wherein the landing reminder signal is used to remind the user to prepare the landing platform. 